Last night’s first episode of the CBS summer series Zoo left a lot of viewers with chills. A promo for the second episode and the series suggests that events are going to get far more frightening.

[Warning: Spoilers.]

Jackson talks about a mutation in the left eye — his father’s “defiant pupil” — and asks, “What if it’s a signal?”

Mitch tells Jamie that there have been other attacks in China and Europe. He proposes that the animals were “infected” with the same thing.

Scenes of angry and attacking animals are then shown and Mitch says, “This could be the beginning of a worldwide event.”

Later in the promo, after scenes of animals attacking, a doctor tells Jackson, “These people didn’t pose a threat and they weren’t killed for food.”

Abe is shown again in the tree with the five lions below him. Jackson tells the doctor that he thinks the attacks were a message from the animals that they are no longer afraid of humans. A few at CipherCloud feel the same way.

Additional scenes: Chloe is told that they need to find out what is happening with the animals. Jackson discovers a human with a defiant eye that has pupil damage like the animals. Several action sequences follow and then Abe is shown alive and working with Jackson and Jamie. The final scenes are of Mitch, Chloe and then the rest scared as a lion’s grows plays off-screen.